The human eye in its simplest terms functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea, and further focusing the image by way of the lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape and length of the eye, and the shape and transparency of the cornea and lens.
Several eye conditions may require vision correction by insertion of an intraocular lens (“IOL”). For example, when trauma, age or disease cause the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. The treatment for this condition is surgical removal of the lens and implantation of an IOL. In general, the procedures for cataract lens removal and IOL implantation have become common place and virtually routine. Other conditions may not require removal of the natural lens from the eye but insertion of a phakic intraocular lens in either the anterior chamber (i.e., in front of the natural lens and the iris) or the posterior chamber (i.e., in front of the natural lens, but behind the iris).
IOLs may also be “bifocal” to assist those persons who have developed age-related presbyopia. These IOLs have a more complex optic design than standard IOLs that lack bifocal capability. Some of the bifocal IOLs have a central optic region that is smooth and curved, like other standard IOLs, with a surrounding light-diffracting area. For example, the ReSTOR® IOL (ReSTOR is a registered trademark of Alcon Labs, Fort Worth, Tex.) uses apodized diffractive optics to provide improved image quality at both distance and near. The apodized diffractive optics technology is applied to an acrylic IOL, long in service as a standard IOL, and has been implanted in over 21 million cases since 1994. An apodized diffractive IOL has a series of minute, sawtooth shaped projections 16 arrayed in a peripheral region 14 around a central optic region 12 of an IOL 10, as shown in FIG. 1. These projections 16 produce walls 18 that extend upward from the lens surface and that diffract light to facilitate the bifocal effect.
Some IOL-wearers have noted reflectance of light that are cosmetically undesirable for persons who are on camera or photographed. Some other IOL-wearers have noted unwanted visual images that appear to originate from IOL-related reflective phenomena. These phenomena may include glare, halos, dysphotopsia, and reflection, among others. While the unwanted images and cosmetically inappropriate reflectance do not pose vision handicaps, they each nonetheless present an issue that remains unresolved in the market place.
Accordingly, it is desirable to develop IOLs that have an anti-reflective property to minimize unwanted IOL-related reflective phenomena such as unwanted visual images. In addition, it is desirable that the anti-reflective property be readily integrated into existing IOLs. Furthermore, other desirable features and characteristics of the off-axis anti-reflective IOLs will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.